MAINT: Move export for scipy arm64 helper into main module

This is a follow up to gh-22679 which addressed gh-22673.

The main thing is that we want the functions to be available after
importing NumPy, so they need to be part of multiarray.
However, `npymath` is a static library, so the symbols are not really
exported there.  The former PR did actually work in practice but this
seems like it is technically the right place?

For some reason, I had to add nextafter to be able to do:

    from scipy.spatial.distance import euclidean

with the SciPy 1.9.3 wheels.  SciPy test collection works with this for
the 1.9.3 wheel, so this should be all the symbols hopefully.

numpy/core/include/numpy/npy_math.h

@@ -184,29 +184,21 @@ NPY_INPLACE double npy_atan2(double x, double y);
 #define npy_fmod fmod
 #define npy_floor floor
 #define npy_expm1 expm1
+#define npy_log1p log1p
 #define npy_acosh acosh
+#define npy_asinh asinh
 #define npy_atanh atanh
 #define npy_rint rint
 #define npy_trunc trunc
 #define npy_exp2 exp2
 #define npy_frexp frexp
 #define npy_ldexp ldexp
+#define npy_copysign copysign
 #define npy_exp exp
 #define npy_sqrt sqrt
 #define npy_pow pow
 #define npy_modf modf
 
-#if defined(__arm64__) && defined(__APPLE__)
-/* due to a build problem with scipy, export these as functions */
-NPY_INPLACE double npy_asinh(double x);
-NPY_INPLACE double npy_copysign(double y, double x);
-NPY_INPLACE double npy_log1p(double x);
-#else
-#define npy_asinh asinh
-#define npy_copysign copysign
-#define npy_log1p log1p
-#endif
-double npy_nextafter(double x, double y);
 double npy_spacing(double x);
 
 /*

numpy/core/setup.py

@@ -771,10 +771,6 @@ def get_mathlib_info(*args):
                        join('src', 'npymath', 'ieee754.c.src'),
                        join('src', 'npymath', 'npy_math_complex.c.src'),
                        join('src', 'npymath', 'halffloat.c'),
-                       # Remove this once scipy macos arm64 build correctly
-                       # links to the arm64 npymath library,
-                       # see gh-22673
-                       join('src', 'npymath', 'arm64_exports.c'),
                        ]
 
     config.add_installed_library('npymath',
@@ -1006,6 +1002,10 @@ def get_mathlib_info(*args):
             join('src', 'multiarray', 'textreading', 'stream_pyobject.c'),
             join('src', 'multiarray', 'textreading', 'str_to_int.c'),
             join('src', 'multiarray', 'textreading', 'tokenize.cpp'),
+            # Remove this once scipy macos arm64 build correctly
+            # links to the arm64 npymath library,
+            # see gh-22673
+            join('src', 'npymath', 'arm64_exports.c'),
             ]
 
     #######################################################################

numpy/core/src/npymath/arm64_exports.c

@@ -1,12 +1,14 @@
 #if defined(__arm64__) && defined(__APPLE__)
 
 #include <math.h>
-/* 
+/*
  * Export these for scipy, since the SciPy build for macos arm64
  * downloads the macos x86_64 NumPy, and does not error when the
  * linker fails to use npymathlib.a. Importing numpy will expose
  * these external functions
  * See https://github.com/numpy/numpy/issues/22673#issuecomment-1327520055
+ *
+ * This file is actually compiled as part of the main module.
  */
 
 double npy_asinh(double x) {
@@ -20,4 +22,9 @@ double npy_copysign(double y, double x) {
 double npy_log1p(double x) {
     return log1p(x);
 }
+
+double npy_nextafter(double x, double y) {
+    return nextafter(x, y);
+}
+
 #endif